TIME, VOLTAGE AND IONIC CONCENTRATION-DEPENDENCE OF RECTIFICATION OF H-ERG EXPRESSED IN XENOPUS OOCYTES

The rapid delayed rectifier, I-Kr, is believed to have h-erg (human et her-a-go-go related gene) as its molecular basis, A recent study has s hown that rectification of h-eg involves a rapid inactivation process that involves rapid closure of the external mouth of the pore or C-typ e inactivation, We measured the instantaneous current to voltage relat ionship for h-erg channels using the saponin permeabilized variation o f the cut-open oocyte clamp technique, In contrast to C-type inactivat ion in other voltage-gated KC channels, the rate of inactivation was s trongly voltage dependent at depolarized potentials, This voltage depe ndence could be modulated independently of activation by increasing [K +](o) from 2 to 98 mM, These results suggest that inactivation of h-er g has its own intrinsic voltage sensor.